package/libsigrok: update musl patch

Upstream chose a different fix:
http://article.gmane.org/gmane.comp.debugging.sigrok.devel/1951



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>